Abstract: Objective To investigate the clinical presentations, serological features, and histopathological characteristics of IgG4-related autoimmune hepatitis (IgG4-AIH). Methods We collected and analyzed the clinical presentations and serological characteristics of 38 patients diagnosed with autoimmune hepatitis (AIH) based on liver tissue histopathology. Liver tissue samples were ssubjected to HE staining as well as immunohistochemical staining for IgG4 to evaluate histological features and the extent of IgG4-positive plasma cell infiltration. Results Among the 38 AIH patients, 7 exhibited elevated serum IgG4 levels and positive liver tissue IgG4 staining, thus categorizing them into the IgG4-AIH group. The remaining 31 cases were considered part of the classic AIH group. Common symptoms observed in both groups included jaundice, fatigue, and anorexia, accompanied by liver function abnormalities characerized by elevated levels of ALT and AST. Autoantibody ANA was detected in 85.7% (6/7) of IgG4-AIH patients, and in 83.8% (26/31) of classic AIH patients. The serum IgG level was significantly higher in the IgG-AIH group (33.2±7.2) compared to the classic AIH group (26.5±5.3). Liver histological inflammation in the IgG4-AIH group was predominantly categorized as G3 and G4, while in the classic AIH group, it mainly fell under G1 and G2. The differences observed between the two groups were statistically significant. Conclusion Serum and liver tissue IgG4 levels were notably elevated in IgG4-AIH patients, with more pronounced inflammatory activity observed in liver pathological examination. Nevertheless, there were no significant difference in clinical manifestations and biochemical indicators between IgG4-AIH and classical AIH patients.

Key words: Autoimmune hepatitis, Ig4, Clinical feature, Pathological feature